1. Field of the Invention
The present invention concerns the fields of computer aided design (CAD) and finite elements analysis (FEA). In particular, the present invention concerns a way of improving the integration of these fields into a unified design environment.
2. Description of Related Art
The use of computer aided design (CAD) techniques has become common engineering practice. The available CAD programs range from simple drawing tools to sophisticated systems covering the whole range of product design and possibly further aspects like engineering or manufacturing or quality control. The term “CAD program” as used herein should therefore be understood in its broadest meaning as any computer program that contains a drawing and/or design component and possibly further components. A widely used CAD program is manufactured in various versions by Autodesk, Inc., San Rafael, USA under the trademark AutoCAD.
Another computer aided technique that has become common practice in the field of mechanical engineering is the technique of finite elements analysis (FEA). FEA is a very powerful numerical method for analyzing mechanical properties of bodies under given load conditions. For example, stress patterns and distributions or the deformation of a body under a load may be calculated and analyzed during the design process without the need for costly experiments. Overviews of the various steps and aspects of FEA can be found in the books “Finite-Element-Analysis, Grundlagen” by R. H. Gallagher, Springer-Verlag, Berlin 1976, and “The Finite Element Method” by O. C. Zienkiewicz and R. L. Taylor, 3rd edition, vol. 1, McGraw-Hill, New York 1977. The disclosure of these books is herewith incorporated in the present specification.
For many available FEA programs, the definition of the input parameters is a rather cumbersome process. While it is normally possible to import data defining the body to be analyzed from a CAD program, load and support parameters must be defined in a complex way. In other words, there is often too little compatibility and integration between independent CAD and FEA programs.
The article “Steps towards CAD-FEA Integration” by S. Arabshahi et al., Engineering with Computers, 1993, vol. 9, no. 1, pages 17–26, discloses an attribute editor using a graphical interface to enable the user to define and attach attributes to different regions of a solid model. A load for an FEA calculation can be assigned to an appropriate region of the model using the graphical interface.
A CAD program with integrated FEA functions is currently available under the trademark Genius Desktop 3 from Autodesk, Inc., San Rafael, USA. This program makes it possible to perform FEA for any three-dimensional body defined using the underlying CAD functionality. The results of the FEA calculations are also displayed for the user in a fully integrated way. However, the Genius Desktop 3 product imposes certain limitations with respect to the definition of load and support parameters (load/support conditions). It is only possible to define forces and fixed and movable supports that act on individual points or along edges or on whole faces (delimited by edges) of the body. These limitations restrict the variety of situations that can be modeled conveniently. Any attempt of the user to work around these limitations would be rather complex and time-consuming, and would furthermore decrease the accuracy of the finite elements analysis and increase the necessary computing time.
Therefore a need exists for improving the integration between CAD programs and FEA programs or program modules. In particular, a need exists for expanding the possibilities for defining parameters like load or support conditions for an FEA calculation in a CAD program. The invention has the objective of meeting these needs fully or at least partially.